The present invention relates to a drill/driver chuck mechanism and to a drill/driver including such a chuck. The invention has particular, although not exclusive, relevance to such a chuck as used on consumer do it yourself products and the like.
Chucks for holding a drill bit or a screwdriver bit have been known for many years. In the do it yourself market, the chucks generally comprise an inner cylindrical hollow core to which a plurality of jaws are held at an angle. The jaws may move into and out of the hollow core thereby clamping a bit therewithin. In order to advance or retract the jaws, the jaws carry a threaded portion. This threaded portion co-operates with a threaded collet member which is generally held circumferentially around the jaws and is able to rotate freely, yet is axially immovable. Thus, on rotation of the collet member, the threads co-operate to advance or retract the jaws.
Whilst the above mode of advancing or retracting the jaws is generally acceptable, it does suffer from some short-coming. In order for the chuck to accommodate different diameter bits, the degree or advancing or retracting of the jaws in order to grip these different diameter bits will vary. Large diameter bits will require the jaws to be retracted further yet not advanced particularly far in order to grip the bit in place. Conversely, a small diameter drill bit will need the jaws advanced a relatively long way into the hollow cylinder before gripping the bit. Equally, retraction of the jaws when the bit is of a small diameter need not be particularly far to release the bit.
Generally, the user of the chuck mechanism has to advance or retract the jaws a suitable distance dependent upon the diameter of the bit being grasped.
It is an object of the present invention to alleviate the above short-coming by providing a drill/driver chuck mechanism wherein the degree of advancement or retraction of the jaws is automatically compensated for, yet the force with which the bit is gripped by the jaws is not dependent upon this advancement or retraction. According to the present invention, therefore, there is provided a drill/driver chuck mechanism including:
a cylindrical member having a central axial bore and a plurality of further bores, such that the plurality of further bores are slanted with respect to the axis of the cylindrical member, and co-operate with the central axial bore;
a plurality of jaws, each jaw being associated with a respective one of the further bores and moveable therewithin;
a jaw actuator, coupled to each of the jaws of the plurality, for moving the jaws within their respective further bores;
and jaw locking means arranged to lock the jaws in a predetermined position within their respective bores;
the chuck mechanism characterised by the jaw locking means having an open position and a closed position and wherein, when the jaw locking means is in the open position the jaws are retracted within their respective bores and do not protrude within the central axial bore, and wherein when the jaw locking means is in the closed position, the jaws are locked within their respective bores regardless of the degree of protrusion of the jaws into the central axial bore.
Preferably, the jaw locking means comprises a handle actuable to move between the open position and the closed position. This allows ease of use of the mechanism for a do it yourself enthusiast.
Additionally, or alternatively, the jaw locking means is operatively coupled to the jaw actuator and causes the jaw actuator to move along the axis of the cylindrical member when the jaw locking means is moved between the open position and the closed position. This allows a straight line advancing or retraction of the jaws, without the need for any rotation about the central axial bore.
Advantageously the handle is coupled to a pivotable actuator able to pivot under action of the handle moving between the open position and the closed position, thereby to advance or retract the jaws within their respective bores. Furthermore the pivotable actuator may cause axial movement of the jaw actuator.
Preferably the jaw locking means has an over-centre locking arrangement. This allows for rigid clamping of the jaws about a bit.
Advantageously the jaw locking means includes adjustable biasing means for setting the extent of protrusion of the jaws within the central axial bore. Furthermore the jaw locking means may include a pair of co-operable wedge members able to lock against each other.